Method for removing paint from painted articles



J. S. JUDD Sept. 14, 1954 METHOD FOR REMOVING PAINT FROM PAINTED ARTICLES Filed Nov. 10, 1948 Inf/E27 7211- Patented Sept. 14, 1954 METHOD FOR REMOVING PAINT FROM PAINTED ARTICLES John S. Judd, Birmingham, Mich., assignor to Lyon, Incorporated, Detroit, Mich., a corporation of Michigan Application November 10, 1948, Serial No. 59,385

2 Claims. 1

The present invention relates to a method for removing foreign deposits from coated objects, and more particularly to a continuous process for removing paint from painted objects.

The removal of paint from objects such as painting masks on a large industrial scale has always been expensive and time-consuming. When a large number of individual pieces are to be cleaned, it is highly impractical to scrub each individual piece with caustic in view of the time consumed in such an operation. When organic solvents are used, these solvents present a problem in fume disposal, since normal paint-removing solvents are somewhat noxious and cannot be tolerated in the atmosphere of the industrial plant.

An object of the present invention is to provide a method whereby individual painted objects may be freed of encrusted paint in a continuous system.

Another object of the present invention is to provide a method for removing paint from painted objects without permitting any substantial escape of noxious fumes from the paint-removing system.

A still further object of the present invention is to provide a method of removing paint from painted objects wherein the loss of the paintremoving solvent is minimized.

As a feature of the present invention, I provide a closed system for removing paint from painted surfaces wherein the object to be cleaned is first contacted with a paint-removing solvent in liquid form, and subsequently contacted with the same solvent in vaporous form.

Another feature of the present invention resides in the provision of liquid seals between the various stages of the process, thereby isolating the various stages and preventing the paint-removing solvent from circulating through the system and thereby interfering with heat transfer conditions.

In accordance with the present invention, the objects to be cleaned are passed through an inlet chamber, and thence through a liquid body of paint-removing solvent which forms a liquid seal between the inlet chamber and a succeeding spray section. Passage of the object through the first liquid body serves to wet the painted surface and loosen paint incrustations. After immersion in the liquid body, the object is passed into the spray section where it is contacted with a cold spray of solvent which serves to loosen or remove substantial quantities of the encrusted paint. After leaving the cold spray section, the object is passed into a second pool of liquid paint-remover which serves as a liquid seal between the spray section on one side and a hot vapor section on the other. Passage of the object through the second body of liquid serves to remove substantially all of the paint which has been previously loosened and dissolved. After passage through the second liquid seal, the object is next contacted with hot vapors of the paint-removing solvent in a hot vapor zone. By contacting the object with hot vapors of solvent, evaporation of a substantial portion of the solvent clinging to the object is effected. After passage through the hot vapor section, the object is next passed through a cooling section where the object is cooled so that it may be handled easily, and any vapors carried from the hot vapor section are condensed and returned to the vapor zone.

In stripping paint from newly painted objects, it is important that the temperature of the object and of the paint be kept at a low value so that the paint does not set upon the mask. Once the paint is set up on the mask, the paint solvent will not remove it, and the object will have to be stripped in the conventional caustic tanks. In the present invention I have provided a method where the actual contacting with the paint solvent is carried out at controlled relatively cool temperatures. The object is heated to a substantial degree only in the hot vapor region, when the paint has already been substantially or completely removed.

As the solvent in the present process I prefer to use the trichloroethylene, although other solvent such as benzene, toluene, xylene, butyl dictate and butyl lactate, or mixtures thereof, may also be used.

A further description of the present invention will be made in conjunction with the attached drawing which illustrates an apparatus adapted for carrying out the process of the present invention, and in which:

The figure is a schematic cross-sectional view of one embodiment of the present invention and illustrates four objects at various stages in the paint removal process.

As shown on the drawing:

Reference numeral [0 denotes in general a housing for the paint-removing assembly whose base portion is formed into an inclined wall H, base portion I2, inclined walls l3, M and [5, base portion I6, upstanding walls I1 and i8 joined by cross member [9, base portion 20, and inclined wall 2|.

Extending the full transverse Width of housing l are a series of bafiie plates including a slotted inlet bafile 22, a solid baffle 23, a slotted bafile 24, a solid baffle 25, and slotted baffles 26, 21, and 28. Extending the length of the housing I0 and supported therein is an arcuate track 29 which may be formed into a generally sinusoidal configuration as shown in the figure. Track 29 supports a roller 30 mounted on an arm 3| which in turn supports the object or work piece 32 from which the paint is to be removed. Roller 30 is free to move along track 29 through the various treating chambers as will be hereinafter described.

The figure shows the condition where four separate work pieces are being treated in various stages of the paint-removing process. Commencing at the inlet end of the assembly, the work piece 32, supported by means of arm 3| which in turn is pivoted on roller 39, passes through a slot which is formed in the inlet baffle 22, permitting the passage of the supported work piece through the bafiie with only a small clearance. After passage through baiiie 22, the work piece 32 is passed through an inlet chamber 33 which is defined by slotted baffle 22, sloping base wall l, base portion l2, and solid baifie 23.

As shown on the drawing, the inlet baffle 22, the inclined wall II, the base portion l2, and the inclined wall |3 define a container for a body of relatively cool paint solvent 34. The work piece 32 is immersed into this body of paint solvent 34 and is next passed by means not shown into a spray chamber 35 which is defined by the surface of the liquid body 34, solid bafiie 23, slotted baflie 24, and inclined base wall M. It will be apparent that the liquid body 34 functions as a liquid seal to prevent any vapors from chamber 35 passing back into inlet chamber 33.

Disposed within spray chamber 35 are a plurality of perforated pipes 36 which are fed by means of conduit 3's, pump 33, and conduit 39 from the liquid body 34. The object to be cleaned, after immersion in the body 34, is passed in close proximity to the perforations of the perforated pipes 36, so that the work piece 32 is effectively sprayed with liquid paint solvent at the temperature approximating that maintained in liquid body 34.

A large portion of the spray is prevented from running out of the spray chamber 35 by slotted bailie 24, and is conducted back into liquid body 34 by inclined base wall l4. After the spraying operation, the object is passed through the slotted baiiie 2'4 and enters a second body of relatively cool paint solvent 4|? contained between sloping base wall |'5, base portion it, and upstanding wall |7. Disposed within the liquid body 49 are a series of cooling coils 4| which serve to maintain the liquid body 49 at a predetermined temperature below that at which substantial vaporization occurs. The liquid body 40 acts as a liquid seal between spray chamber 35 and a hot vapor chamber 42, thus minimizing the transfer of heat and vapor between the two chambers.

The work piece 32' after immersion in the liquid body 40 is next passed through a slotted baffle 25 and into a hot vapor chamber 42 defined by the slotted bailie 26, a slotted baffle 21, and a body of relatively hot pain-t solvent 43. The heated liquid body 43 is contained between the upstanding wall 58, base portion 26, and wall 45. Disposed within the heated liquid body 43 are a series of heating coils 44 which serve to impart a temperature to the liquid body 43 sufiicient to vaporize a substantial part of the liquid body thus maintaining a concentration of heated vapors in vapor chamber 42 sufficient to heat the object as it passes through the chamber 42. In the configuration shown in the drawing, heating coils 44 are insulated from cooling coils 4| by providing a dead air space 46 defined by walls l8 and cross member I9 between the two sets of coils. In the vapor chamber 42, the work piece 32 is contacted with the heated vapors rising from the liquid body 43 which serve to heat the work piece 32 and evaporate a major portion of the solvent clinging to the work piece 32. After treatment in the vapor chamber 42, the work piece 32 is next passed through the slotted bafiie 21 and diagonally through the space enclosed by a bank of condensing coils 41.

As shown on the drawing, the bank of cooling coils 41 is inclined slightly to the horizontal. The higher end of the bank of coils 41 is formed to permit passage of the object 32 therethrough as by forming the bank 46 into a series of interconnected U-shaped tiers disposed on parallel planes. The object 32 thus enters the bank of condensing coils 41 near the base thereof and passes upwardly through the space enclosed by the cooling coils and emerges over the lower rear end of the bank of condensing coils 41. The bank of cooling coils 4'! serves the function of condensing any vapors occluded on the work iece 32 from the vapor chamber 42 as well as any extraneous vapors escaping from the vapor chamber 42. The condensed liquid is then re turned to vapor chamber 42 by means of inclined base wall 2| through a suitable slot at the base of the slotted baffle 21. The cooled object, after contact with the bank of cooling coils 46, is removed from the system through the slotted exit baffle 28 in a clean, dry, and relatively cool condition.

When trichloroethylene is used as the paint solvent, the liquid bodies 34 and 40 will normally be maintained at a temperature below F. to prevent vaporization of the solvent. The heated liquid body 43 will be maintained at a temperature of about F. in the case of trichloroethylene, or in any event, somewhat below the boiling point of the solvent used, so that substan tial vaporization is effected in the vapor cham' ber 42.

It can thus be seen that I have provided a method and apparatus for removing paint from newly painted objects wherein the various treat-- ing steps are isolated by means of liquid seals, and have further provided a simple, efficient and continuous process for removing paint from newly painted objects which may be carried out in a large scale operation.

While the above description has been concerned primarily with paint removal, it will be apparent that the method of apparatus can also be used for the removal of deposits such as tar and the like.

It is evident that many modifications may be made to the method disclosed herein, and it is not my intention to limit the invention to the single embodiment shown but limited merely asnecessitated by the scope of the appended claims.

I claim as my invention? 1. The method of removing paint froma' paint ed object which comprises immersing said obiect in a body of cold liquid paint solvent, sprayingv the object with cold liquid paint solvent in a spraying zone, pass-ing the sprayed object into a. second liquid body of cold paint solvent, pass ing the object from said second body into a vapor zone, contacting said object with heated vapors of said solvent in said vapor zone to heat said object, and passing the heated object into a cooling zone to condense vapors from said vapor zone.

2. A process for removing paint from a painted object which comprises immersing said object in a bath of liquid tri-chloroethylene maintained at a temperature below 140 F., passing the object from said zone into a spray zone, spraying the object in said spray zone with 1iquid triohloroethylene, immersing the sprayed object into a second body of liquid trichloroethylene maintained at a temperature below 140 F., passing the object from said second body into a vapor zone, contacting said object with heated vapors of trichloroethylene in said vapor zone to heat said object, and passing the heated object into a cooling zone to condense vapors from said vapor zone.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,101,840 Dinley Dec. 14, 1937 2,113,129 Dinley Apr. 5, 1938 2,118,480 Somes May 24, 1938 2,134,602 Cohen Oct. 25, 1938 2,201,729 Hood May 21, 1940 2,255,493 Pfalzgraif Sept. 9, 1941 2,270,642 Somes Jan. 20, 1942 2,273,939 Dammers Feb. 24, 1942 2,495,729 Hutson Jan. 31, 1950 

1. THE METHOD OF REMOVING PAINT FROM A PAINTED OBJECT WHICH COMPRISES IMMERSING SAID OBJECT IN A BODY OF COLD LIQUID PAINT SOLVENT, SPRAYING THE OBJECT WITH COLD LIQUID PAINT SOLVENT IN A SPRAYING ZONE, PASSING THE SPRAYED OBJECT INTO A SECOND LIQUID BODY OF COLD PAINT SOLVENT, PASSING THE OBJECT FROM SAID SECOND BODY INTO A VAPOR ZONE, CONTACTING SAID OBJECT WITH HEATED VAPORS OF SAID SOLVENT IN SAID VAPOR ZONE TO HEAT 